1. Field of the Invention
The present invention relates to an electronic device, an electronically-controlled, mechanical timepiece, and an electronic device controlling method. More specifically, the present invention relates to such a device/timepiece which includes a mechanical energy source, a generator which is driven by the mechanical energy source and which generates induced electrical power and provides electrical energy, and a rotation controller which is driven by the electrical energy and which controls the rotation period of the generator. A method for so controlling an electronic device is also provided.
2. Description of the Related Art
Japanese Patent Publication No. 7-119812 discloses an electronically controlled, mechanical timepiece which presents precise time by accurately driving hands attached to a gear train. In this timepiece, a mainspring, when unwound, releases mechanical energy, which is converted into electrical energy by a generator. The electrical energy is then used to drive a rotation controller, which controls the current flowing through a coil of the generator.
In order to increase the duration of such an electronically-controlled, mechanical timepiece, it is important that, while a torque of the mainspring (mainspring torque) is high, a braking torque can be increased without reducing the power generated. More specifically, in the brake control of the generator, preferably, the braking torque is prioritized when the mainspring torque is high and power generation (electromotive force) is prioritized when the mainspring torque is low, that is, when a large braking force is not required. The torque (mainspring torque) is increased not only when the mainspring is wound by a large amount but also when a driving torque applied to a rotor is increased due to external shock such as oscillation, impact, etc. Similarly, the torque (mainspring torque) is increased not only when the mainspring is loose but also when the driving torque applied to the rotor is reduced due to the external shock.
Thus, according to the Japanese Patent Publication No. 7-119812, two angular ranges are provided in a single turn of a rotor, that is, in each period of a reference signal. In one angular range, a braking force is removed to increase the rotational speed of the rotor so that the amount of power generation is increased. In the other angular range, a braking force is applied to reduce the rotational speed of the rotor. The efficiency in power generation is increased while the rotor rotates at a high speed to compensate for a drop in power generation that takes place during the braking period.
More specifically, according to the Japanese Patent Publication No. 7-119812, the braking force is removed at first time points which occur periodically at the same period as a reference signal obtained from a crystal oscillator, etc. In addition, the braking force is re-applied at second time points, which occur alternately with the first time points with the same period as the reference signal. Accordingly, the braking force is removed and re-applied in every period of the reference signal. However, according to the Japanese Patent Publication No. 7-119812, power generation is reduced while the braking force is applied, so that there is a limit to the amount by which the braking torque can be increased while the reduction in power generation is suppressed.
In addition, according to the Japanese Patent Publication No. 7-119812, the braking force is simply applied or removed. Thus, the rotational speed of the rotor is suddenly reduced when the braking force is applied and is suddenly increased when the braking force is removed. A problem with this arrangement is that the sudden changes in the rotational speed of the rotor cause the hands connected to the rotor vibrate at a large amplitude. In addition, since the braking force is simply applied or removed, an excessive braking force may be applied even when only a small braking force is required, and the braking force may be reduced too much even when only a small reduction is required.
Especially when an excessive braking force is applied, the possibility that the rotor will stop due to a cogging torque of the rotor increases. For example, according to experiments performed by the inventors, if a generator of an electronically-controlled, mechanical timepiece is controlled to rotate at 8 Hz, the possibility that a rotor will stop due to the cogging torque increases when the rotational speed is reduced to 5 Hz by the braking force.
In contrast, when the braking force is reduced too much, there is a problem in that the rotational speed of the rotor is excessively increased.
These problems occur not only in electronically-controlled, mechanical timepieces, but also in various electronic devices such as music boxes, metronomes, etc., which include components rotated by a mechanical energy source such as a mainspring, an elastic band, etc. Thus, solving these problems would improve these timepieces and electronic devices.
An object of the present invention is to provide an electronically-controlled mechanical timepiece, an electronic device and a method for controlling such a device, which overcome these problems.
It is another object of this invention to provide such a timepiece, device and controlling method in which the braking torque can be increased while the reduction in power generation is suppressed, in which the variation in rotational speed of the rotor of the generator can be reduced, and in which the rotational speed of the rotor can be reliably controlled while preventing the rotor from stopping or rotating at an excessive speed.
According to one aspect of the present invention, an electronic device is provided. Such a device comprises a mechanical energy source; a generator configured to be driven by the mechanical energy source, to generate induced electrical power, and to provide electrical energy; and a rotation controller configured to be driven by the electrical energy, and to control the rotation period of the generator. The rotation controller includes a switch that is able to selectively connect both terminals of the generator in the form of a closed loop, a chopping signal generator configured to generate a chopping signal that is applied to the switch for brake control of the generator, and a brake controller configured to control the chopping signal generator, and thereby control a braking force applied to the generator, by switching between at least three brake control modes, including a high-power brake control mode in which an effective braking force is large, a mid-power brake control mode in which the effective braking force is less than the effective braking force of the high-power brake control mode, and a low-power brake control mode in which the effective braking force is less than the effective braking force of the mid-power brake control mode.
In the electronic device of the present invention, the generator is driven by the mechanical energy source, which may be a mainspring or equivalent component, and the rotational speed of a rotor in the generator is controlled by applying a braking force to the generator, as determined by the rotation controller.
The rotation of the generator is controlled by applying the chopping signal to the switch, that is, by turning on and off the switch, which selectively connects both terminals of a coil of the generator in the form of a closed loop. When the switch is turned on, both terminals of the generator coil are connected in the form of a closed loop so that a short brake is applied and energy is stored in the coil of the generator. When the switch is turned off and the loop is opened, the generator is activated. Because of the additional energy stored in the coil, the electromotive force (generated voltage) of the generator is increased. Since the brake control is performed based on the chopping signal, in the case in which a large braking force is applied, the reduction in power generation can be compensated for by the increase of electromotive force during the time in which the switch is turned off. Accordingly, the braking force (braking torque) can be increased while the reduction of power generation is suppressed to provide an electronic device having a long duration.
Further, by employing at least three braking modes, situations where an excessive braking force is applied when only a small braking force is required or where a braking force is reduced too much when only a small reduction is required can be avoided. Thus, the generator is prevented from stopping because of an excessive braking force and is also prevented from rotating at a speed higher than the reference speed because of excessive reduction of the braking force. Accordingly, the rotational speed of the generator can be maintained relatively constant.
The closed loop state is one in which the braking force applied to the generator is relatively increased. Thus, a circuit including, for example, a resistance element between the switch and the generator may also be regarded as a closed loop. However, the terminals of the generator are preferably directly shorted since the potentials at the terminals of the generator can be easily made the same and the short brake can be effectively applied. The chopping signal obtained from the chopping signal generator may be directly input to the switch or be input to the switch via other circuits or elements.
Preferably, the chopping signal generator is able to generate at least three chopping signals, each having a different duty factor or different frequency than the others, to generate different effective braking forces depending on which chopping signal is applied to the switch, and the brake controller includes a chopping signal selector which selects one of the at least three chopping signals to be applied to the switch.
The effective braking force can also be changed by attaching a variable resistor to the coil circuit to which the chopping signal is applied and changing the resistance of the coil. However, when the effective braking force is changed using at least tree chopping signals, each of which differ in at least one of the duty factor and the frequency, as described above, the circuit construction can be simplified and the rotation control can be more easily performed. In addition, the short brake can be more effectively applied.
As described above, the chopper control of the generator is performed by providing the switch that is able to connect both terminals of the generator in the form of a closed loop and applying the chopping signal to the switch. In such a case, the driving torque (braking torque) increases as the chopping frequency is reduced, and as the duty factor is increased. In addition, the charging voltage (generated voltage), that is, the electromotive force, increases as the chopping frequency is increased, but decreases only by a small amount even when the duty factor is increased. When the frequency is 50 Hz or more, the charging voltage increases until the duty factor reaches 0.8. Thus, the chopping signals for the high-power brake control, the mid-power brake control, and the low-power brake control can be determined in consideration of the above-described characteristics.
Also, according to the present invention, the mid-power brake control may be advantageously performed in a transitional period between which the low- and high-power brake control modes are performed. That is, before switching from the low- to the high-power braking mode or vice versa, mid-power brake control is performed.
By not suddenly switching from the low-power brake control mode to the high-power brake control mode but instead first switching to the mid-power brake control mode and then to the high-power brake control mode, the risk of generating excessive braking force causing the rotor of the generator to stop can be prevented. In the generator, the problem of the rotor stopping is more critical than the problem of the rotor rotating at an excessive speed. Thus, the rotational speed of the generator can be more reliably controlled by performing the mid-power brake control before the high-power brake control.
By not suddenly switching from the high-power brake control mode to the low-power brake control mode but instead first switching to the mid-power brake control mode and then to the low-power brake control mode, excessive reduction of the braking force can be more reliably prevented. Accordingly, the situation such that the phase of the rotor exceeds that of the reference signal and the rotor rotates at an excessive speed can be prevented and the rotational speed of the generator can be reliably controlled.
Most preferably, the mid-power brake control is performed in a transitional period during which the low-power brake control is switched to the high-power brake control and also in a transitional period during which the high-power brake control is switched to the low-power brake control. By performing the mid-power brake control in both of the above-described transitional periods, over increase and over reduction of the braking force can be prevented. Thus, the rotor can be prevented from stopping and the rotational speed of the rotor can be more reliably maintained constant.
According to another aspect of the present invention, an electronic device comprises a mechanical energy source; a generator configured to be driven by the mechanical energy source, to generate induced electrical power, and to provide electrical energy; and a rotation controller configured to be driven by the electrical energy, and to control the rotation period of the generator. The rotation controller includes a switch which is able to selectively connect both terminals of the generator in the form of a closed loop, a chopping signal generator configured to generate a chopping signal that is applied to the switch for brake control of the generator, and a brake controller configured to control the chopping signal generator, and thereby control a braking force applied to the generator, by selectively switching between a high-power brake control mode in which an effective braking force is gradually increased and a low-power brake control mode in which the effective braking force is gradually reduced.
Since the effective braking force is gradually changed in each of the high- and low-power brake control modes, the braking force applied to the generator does not suddenly change by a large amount. Thus, the rotational speed of the rotor can be gradually changed and the reliability of the rotation control can be improved. As a result, the rotational speed can be maintained constant while the generator is prevented from stopping because of an excessive braking force or rotating at a speed higher than the reference speed because of excessive reduction of the braking force.
In addition, since the brake control is performed based on the chopping signal, the reduction in power generation can be compensated for by the increase of electromotive force during the time in which the switch is turned off. Accordingly, the braking force (braking torque) can be increased while the reduction of power generation is suppressed to provide an electronic device having a long duration.
Preferably, the chopping signal generator is able to generate a plurality of chopping signals, each having a different duty factor or different frequency than the others, to generate different effective braking forces depending on which chopping signal is applied to the switch, and the brake controller includes a chopping signal selector which sequentially selects one of the chopping signals to be applied to the switch.
When the effective braking force is changed using a plurality of chopping signals, each differing in at least one of the duty factor and the frequency, the circuit construction can be simplified and the rotation control can be more easily performed, as compared to the case in which the effective braking force is changed by changing a circuit resistance. In addition, the short brake can be more effectively applied.
Preferably, when the low-power brake control mode is switched to the high-power brake control mode, the effective braking force is gradually increased from a predetermined value to avoid a sudden and large increase in the applied braking force. Accordingly, the rotor of the generator can be reliably prevented from stopping because of an excessive braking force.
In addition, preferably, when the high-power brake control mode is switched to the low-power brake control mode, the effective braking force is gradually reduced from a predetermined value to avoid a sudden and large decrease in the applied braking force. Accordingly, the rotor of the generator can be prevented from rotating at a high speed because of excessive reduction of the braking force and the rotational speed of the generator can be reliably controlled.
The braking forces applied at the start of the high-power brake control and at the start of the low-power brake control, respectively, may be determined in accordance with the application. For example, the predetermined braking force may be fixed in advance to a value between a maximum effective braking force and a minimum effective braking force. More specifically, in the case in which the effective braking force is changed by switching the duty factor of the chopping signal in fifteen steps in the range of {fraction (1/16)} to {fraction (15/16)}, the duty factor of {fraction (7/16)} or {fraction (8/16)} may be used as the duty factor at the start of the high- or low-power brake control. Then, when the high-power brake control is continuously performed, the duty factor is gradually increased so that the effective braking force is also gradually increased. On the other hand, when the low-power brake control is continuously performed, the duty factor is gradually reduced from that starting factor so that the effective braking force is also gradually reduced.
When the effective braking force applied at the start of the high-power brake control mode and the low-power brake control mode is set to a fixed value in advance, the braking force applied to the generator can be predicted in advance, thus simplifying the brake control method and a program for implementing it. The predetermined value may be determined on the basis of the effective braking force which is applied immediately before the brake control mode is switched. More specifically, when the high-power brake control mode is switched to the low-power brake control mode, an effective braking force that is less than that applied at the end of the high-power brake control mode may be applied at the start of the low-power brake control mode. Then, when the low-power brake control mode is continuously performed, the effective braking force may be gradually reduced. Similarly, when the low-power brake control mode is switched to the high-power brake control mode, an effective braking force that is greater than that applied at the end of the low-power brake control mode may be applied at the start of the high-power brake control mode. Then, when the high-power brake control mode is continuously performed, the effective braking force may be gradually increased. Accordingly, the change in the effective braking force when the brake control mode is switched between the high- and the low-power brake control modes can be reduced, and the rotational speed of the rotor can be more smoothly changed.
According to another aspect of the present invention, an electronic device comprises a mechanical energy source; a generator configured to be driven by the mechanical energy source, to generate induced electrical power, and to provide electrical energy; and a rotation controller configured to be driven by the electrical energy, and to control the rotation period of the generator. The rotation controller includes a switch which is able to selectively connect both terminals of the generator in the form of a closed loop, a chopping signal generator configured to generate a chopping signal that is applied to the switch for brake control of the generator, and a brake controller configured to control the chopping signal generator, and thereby control a braking force applied to the generator, by selectively switching between at least two brake control modes, including a high-power brake control mode in which an effective braking force is large and a low-power brake control mode in which the effective braking force is less than the effective braking force of the high-power brake control mode, and which gradually changes the braking force in at least one of the high-power brake control mode and the low-power brake control mode.
As described above, the effective braking force is gradually changed in at least one of the high- and low-power brake control modes. Thus, the braking force applied to the generator does not suddenly change by a large amount, as in the case in which a substantial braking force is simply applied or removed all at once. Thus, the rotational speed of the rotor can be gradually changed and the reliability of the rotation control can be improved. As a result, the generator can be prevented from stopping because of an excessive braking force or rotating at a speed higher than the reference speed because of excessive reduction of the braking force.
In addition, since the brake control is performed based on the chopping signal, the reduction in power generation can be compensated for by the increase of electromotive force during the time in which the switch is turned off. Accordingly, the braking force (braking torque) can be increased while the reduction of power generation is suppressed to provide an electronic device having a long duration.
Preferably, when the braking force is gradually changed, the braking force starts at a predetermined value. When the effective braking forces applied at the start of the high- and low-power brake control modes are respectively set to predetermined values in advance, the braking force applied to the generator can be predicted in advance. Thus, a program, etc., for the brake control can be made simpler.
According to another aspect of the present invention, an electronically-controlled, mechanical timepiece comprises a mechanical energy source; a generator configured to be driven by the mechanical energy source, to generate induced electrical power and to provide electrical energy; a time display configured to be operated in association with the rotation of the generator; and a rotation controller configured to be driven by the electrical energy, and to control the rotation period of the generator. The rotation controller includes a switch which is able to selectively connect both terminals of the generator in the form of a closed loop, a chopping signal generator configured to generate a chopping signal that is applied to the switch for a brake control of the generator, and a brake controller configured to control the chopping signal generator, and thereby control a braking force applied to the generator, by switching between at least three brake control modes, including a high-power brake control mode in which an effective braking force is large, a mid-power brake control mode in which the effective braking force is less than the effective braking force of the high-power brake control mode, and a low-power brake control mode in which the effective braking force is less than the effective braking force of the mid-power brake control mode.
According to another aspect of the present invention, an electronically-controlled, mechanical timepiece comprises a mechanical energy source; a generator configured to be driven by the mechanical energy source, to generate induced electrical power, and to provide electrical energy; a time display configured to be operated in association with the rotation of the generator; and a rotation controller configured to be driven by the electrical energy, and to control the rotation period of the generator. The rotation controller includes a switch which is able to selectively connect both terminals of the generator in the form of a closed loop, a chopping signal generator configured to generate a chopping signal that is applied to the switch for a brake control of the generator, and a brake controller configured to control the chopping signal generator, and thereby control a braking force applied to the generator, by switching between a high-power brake control mode in which an effective braking force is gradually increased and a low-power brake control mode in which the effective braking force is gradually reduced.
According to another aspect of the present invention, an electronically-controlled, mechanical timepiece comprises a mechanical energy source; a generator configured to be driven by the mechanical energy source, to generate induced electrical power, and to provide electrical energy; a time display configured to be operated in association with the rotation of the generator; and a rotation controller configured to be driven by the electrical energy, and to control the rotation period of the generator. The rotation controller includes a switch which is able to selectively connect both terminals of the generator in the form of a closed loop, a chopping signal generator configured to generate a chopping signal that is applied to the switch for a brake control of the generator, and a brake controller configured to control the chopping signal generator, and thereby control a braking force applied to the generator, by switching between at least two brake control modes, including a high-power brake control mode in which an effective braking force is large and a low-power brake control mode in which the effective braking force is less than the effective braking force of the high-power brake control mode, and to gradually change the effective braking force in at least one of the high-power brake control mode and the low-power brake control mode.
In the electronically-controlled, mechanical timepiece of the present invention, the rotational speed can be maintained constant while the generator is prevented from stopping because of an excessive braking force and is also prevented from rotating at a speed higher than the reference speed because of excessive reduction of the braking force. Thus, rotation control can be reliably performed. Moreover, since the rotor can be steadily moved, vibration of hands that are moved in association with the rotor can be suppressed. Accordingly, a high quality electronically-controlled, mechanical timepiece can be provided.
According to another aspect of the present invention, a method for controlling an electronic device is provided. The device includes a mechanical energy source; a generator configured to be driven by the mechanical energy source, to generate induced electrical power, and to provide electrical energy; and a rotation controller configured to be driven by the electrical energy and to control the rotation period of the generator. The method comprises the steps of applying a chopping signal to a switch which is able to selectively connect both terminals of the generator in the form of a loop; and controlling the applying of the chopping signal, and thereby controlling a braking force applied to the generator, by switching between at least three brake control modes, including a high-power brake control mode in which an effective braking force is large, a mid-power brake control mode in which the effective braking force is less than that of the high-power brake control mode, and a low-power brake control mode in which the effective braking force is less than that of the mid-power brake control mode.
According to another aspect of the present invention, a method for controlling an electronic device is provided. The device includes a mechanical energy source; a generator configured to be driven by the mechanical energy source, to generate induced electrical power, and to provide electrical energy; and a rotation controller configured to be driven by the electrical energy and to control the rotation period of the generator. The method comprises the steps of applying a chopping signal to a switch which is able to selectively connect both terminals of the generator in the form of a loop; and controlling the applying of the chopping signal, and thereby controlling a braking force applied to the generator, by switching between a high-power brake control mode in which an effective braking force is gradually increased and a low-power brake control mode in which the effective braking force is gradually reduced.
According to another aspect of the present invention, a method for controlling an electronic device is provided. The device includes a mechanical energy source; a generator configured to be driven by the mechanical energy source, to generate induced electrical power, and to provide electrical energy; and a rotation controller configured to be driven by the electrical energy and to control the rotation period of the generator. The method comprises the steps of applying a chopping signal to a switch which is able to selectively connect both terminals of the generator in the form of a loop; and controlling the applying of the chopping signal, and thereby controlling a braking force applied to the generator, by switching between at least two brake control modes, including a high-power brake control mode in which an effective braking force is large and a low-power brake control mode in which the effective braking force is less than that of the high-power brake control mode; and gradually changing the braking force in at least one of the high-power brake control mode and the low-power brake control mode.
According to the above-described control methods, the rotational speed can be maintained constant while the generator is prevented from stopping because of an excessive braking force and is also prevented from rotating at a speed higher than the reference speed because of excessive reduction of the braking force. Thus, rotation control can be more reliably performed.